The field of this invention includes ring lasers used in laser gyros, which are typically used in system applications to measure rotation. The concept of using a ring laser to measure angular motion (rotation) was first publicly disclosed in the Feb. 11, 1963 Aviation Week and Space Technology magazine. Its operation was based on using a low pressure Helium-Neon gas discharge for the active gain medium for good technical reasons and ring laser gyros have been powered by an Helium-Neon gas discharge ever since. For more than 50 years no better method has been found. The physics of gas discharge and solid state lasers is now well understood (see, for example, Yariv, and Rabeendran) and gas discharge ring laser gyros are now used successfully in navigation, stabilization, surveying and many other systems. They work very well but have lifetime, reliability, performance and size limitations associated with the gas discharge and are expensive to manufacture. The gain mirror described below for use in a truly solid state ring laser will have a very positive impact on all these areas.    Klass, P. J., Ring Laser Device Performs Rate Gyro Angular Sensor Functions, Aviation Week and Space Technology Magazine, Feb. 11, 1963    Yariv, A., Introduction to Optical Electronics, 2nd Ed., New York, Holt, Rhinehart and Winston, 1976    Rabeendran, N., New Approaches to Gyroscopic Lasers, PhD Thesis, University of Canterbury, 2013